The present invention relates to an air-bag, and more particularly relates to an air-bag adapted to be inflated to high pressure. The present invention also relates to a method of making an air-bag.
It has been proposed to provide air-bags in various locations within a motor vehicle. Each air-bag is adapted to be inflated in the event that an accident should occur to provide protection for an occupant of the vehicle. Some air-bags are subjected to extremely high forces during a collision, especially when the occupant of the vehicle strikes the air-bag with parts of their anatomy which present only a very small contact surface to the air-bag. For example, an air-bag which is located in a motor vehicle in front of the knees of the occupant, may be subjected to a very high force when an occupant moves forwardly relative to the air-bag and strikes the air-bag with their knees, due to the fact that knees are relatively “pointed”, and thus only present a small area of contact with the air-bag. In such a situation there can be a tendency for the knees of the occupant to force the material or fabric at the front of the inflated air-bag towards the back of the airbag. Thus there is a risk that, in this way, the knees of the occupant will effectively pass right through the air-bag and engage with the structure on which the air-bag is mounted.
The risk of parts of an occupant passing “through” an inflated air-bag in this way is especially high if the air-bag is “flat”, which means to say that the air-bag is of such a design that it does not have a substantial thickness, when inflated, as compared with its face area. Air-bags of this type may be considered to be “two-dimensional” as opposed to a more conventional substantially spherical air-bag which may be considered to be “three-dimensional”.
It would be possible to minimise the risk of parts of an occupant of a vehicle extending “through” an air-bag by providing a substantially rigid load-distribution element on the front face of the air-bag. However, this expedient is relatively expensive. Also it would be possible to utilise a three-dimensional air-bag instead of a two-dimensional air-bag, but three-dimensional air-bags are more expensive to manufacture.
A further solution would be simply to utilise a two-dimensional air-bag which, when inflated, is inflated to a very high pressure. However, here the problem is faced that with a high pressure air-bag there is a substantial risk for gas leakage, especially in the corner region of the air-bag where it is difficult to effect a good seal. Thus gas may be concentrated or trapped in the corner areas, and may escape from the air-bag, especially during inflation of the air-bag.
The present invention seeks to provide an improved air-bag.